This work will study the effects of common loading environments on the mechanical properties of the human lumber intervertebral motion segment. The eventual goal of this work is to establish an "envelop" of loading conditions which should not be exceeded if the spine is to experience minimal mechanical change. Mechanical property characteristics of the specimens will be recorded and used as the outcome measures of the tests. A further outcome measure to be used will be the location of the application point of the axial load where resultant lateral bend and flexion-extension coupled rotation is minimized. Outcome measures will be obtained before and after sustained exposure to simulated loading environments (simulated standing, walking,a nd sitting in static or various vibration environments). They will also be obtained after a sudden flexion-compression loading of the specimen. This is designed to study whether it is mechanically deleterious to the motion segment to lift suddenly or to catch a rapidly shifting load. simulations will be performed to study the effect of different static and cyclic loading environments while either in standing or sitting postures. The following null hypotheses will be assessed using a repeated measures analysis of variance: (1) There is no significant difference in mechanical properties of the lumbar motion segment caused by sustained exposure to either standing or sitting loading environments. (2) There is no significant difference in mechanical properties of the lumbar motion segment cause by sustained exposure to either static or various vibration loading environments. (3) There is no significant difference in mechanical properties of the lumbar motion segment after a sudden, flexion-compression overload following sustained exposure to either standing, sitting, static or various vibration loading environments. Using thee hypotheses, it will be possible to differentiate the effects of static and vibration loading and standing and sitting postures on the mechanical properties of the lumbar motion segment. The overall goal is to establish the mechanical effect of load history on the motion segment and to determine whether load history increases the livelihood of significant mechanical derangement following a sudden mechanical overload. This will begin to establish whether the International Standards Organization vibration exposure criteria are reasonable limits for minimizing mechanical changes in the spine.